Book ReviewsOrigins & Design 18:1

Looking for the Mind

The Conscious Mind: In Search of a Fundamental
TheoryDavid J. ChalmersOxford University Press,
1996, 414 pp.

Eric Larson

Perhaps one of the most exciting
trends in current philosophy of mind is the renewed interest in
what David Chalmers calls the really hard problems of consciousness.
"While it was once assumed that the apparently prickly issue
of consciousness would yield fairly easily to advances in neurophysiology
and computational models, as this century draws to a close our
conscious minds remain mysterious. The seeming imperviousness
of consciousness to traditional scientific methods has prompted
not only philosophers but scientists as well to re-evaluate the
facile optimism which characterized the field previously. Chalmers,
in The Conscious Mind, has taken us to the heart of the
current debate.

Chalmers has two aims: he wants to take consciousness seriously,
and he wants to take science seriously. He begins by challenging
the notion--accepting as dogma by most scientists--that conscious
experience can be reductively explained. Pointing out that reductive
explanations explain high-level phenomena by providing a structural
or functional analysis at lower-levels, he asks the simple question:
How could consciousness possibly be explained this way? Here he
draws a distinction between the purely psychologicalthe lower-level
brain activities which accompany consciousnessand the phenomenologicalthe
higher level conscious experiences as they appear to us. With
this distinction, Chalmers argues that reductive explanations
of mind give psychological answers to phenomenological questions.
Phenomenological questions ask about consciousness qua
consciousness, about the particular quality of consciousness considered
in itself, while psychological answers specify systems of neurons
and physical processed within the brain. As explanations of the
same thing, Chalmers believes the two are incommensurable. Given
any psychological explanation of consciousness, the phenomenal
question is always left unanswered: But why does consciousness
have the particular qualities that it does? How can a structure
or function in the brain tell me why red looks red; blue looks
blue; pain have its particular quality in my mind, and so on?
To this question, he concludes, current science cannot speak,
and so, to use the popular phrase of Wittgenstein, it must remain
silent.

At least for now. Chalmers' ultimate goal is to show how an
appropriately expanded science could incorporate consciousness.
To make his case, he must first debunk the doctrine of materialism
itself. Appealing to thought experiments utilizing zombies, inverted
spectrums, and neuron replacement with silicon chips, Chalmers
argues that all of the physical facts about the universe could
be known in detail, while the facts about consciousness could
remain unknown. Consider his zombie twin--an imaginary physical
replica of himself which differs only in that it lacks consciousness.
While he admits that such a being is probably not actually possible,
he argues that it is still logically possible. This seems true
enough. I can imagine a replica of myself, possessing all of the
physical facts about my body and brain down to the smallest detail,
and yet having no consciousness whatever. According to Chalmers,
my zombie twin would act, think, and speak exactly as I do, only
the lights would be off inside. The conclusion? Physical facts
cannot logically entail facts about consciousness, and so materialism--the
doctrine that physical facts must logically entail all facts (since
physical facts are all there is)--cannot be true. As Chalmers puts
it, after God fixed all physical facts about the universe, He
still had more work to do--He had to fix the facts about consciousness.

Chalmers speaks of God in a metaphorical sense. He does not
want to bring back that great bane of contemporary science, the
immaterial mind or soul. What he wants is to consider consciousness
itself as a fundamental property of an expanded, yet still naturalistic,
scientific framework. Just as mass, momentum, and energy are irreducible,
so too is consciousness itself. So if consciousness is to be taken
seriously, science must simply get used to the fact that it is
not a reducible feature of the universe. But the new science will
still do what the old one has done--incorporate the novel property
and find the laws (psychophysical laws, as he calls them) which
relate the property to the rest of the system. All is well.

Not really. One of the straight-away consequences of Chalmers'
argument is the rather unpalatable problem of epiphenomenalism--the
position that our conscious minds are causally influenced by our
physical brains but cannot themselves exert any causal influence.
Chalmers apparently does not see much of a need to take the problem
of epiphenomenalism seriously, commenting that, if his arguments
are sound, then we may simply have to get used to it. A tension
in his work is therefore revealed: epiphenomenalism is counter-intuitive
in the extreme. I do not think, for instance, that when my hand
is burned by a flame, my conscious experience of pain has nothing
to do with the decision to pull my hand away. Indeed, our decisions
and judgments seem to follow directly from our conscious experiences.
According to Chalmers, our intuition that our conscious minds
exert a causal influence on our behavior may turn out to be smoke
and mirrors. His argument is therefore ironic: while he begins
by resolving to take the problems of mind seriously, he ends with
a position that no one can take seriously.

The problem for Chalmers is that he is committed to taking
science seriously as well, which he believes necessitates a belief
in the absolute causal determinacy of the physical world. Science
apparently establishes that the physical world is, as he puts
it, causally closed. Every physical event has a sufficient physical
cause (this is the definition of scientific determinism). From
this, it follows that any influence from the mind is impossible.
Given the premise of causal closure, his argument is consistent.
But thoughtful readers could wonder: Might it be the case that
the physical world is not absolutely determined? Chalmers denies
this possibility emphatically; indeed, the presumption of causal
closure is one of the key constraints of his theory. Whether in
his idealized thought experiments with zombies, or in the real
world of people, Chalmers argues that determinism is part and
parcel of physical reality. What is physical, is determined. While
his initial arguments against materialism are brilliant and persuasive,
his allegiance to determinism becomes problematic. By maintaining
that consciousness is a fundamental property in an expanded physical
domain, it can not act independently of that domain, anymore than
other physical properties such as mass or momentum. There is no
way our conscious minds can act. We are left with epiphenomenalism.
Consciousness may indeed be beyond materialism, but it remains
a passive feature of a physical framework, and as such carries
no causal efficacy. The common thread here is that whatever model
he considers, whether expanded or otherwise, it must remain determined.
To suggest otherwise would be to travel outside the bounds of
science.

But could Chalmers be taking science too seriously? Does it
follow from science that the physical world must be deterministic?
Chalmers evidently takes this position as incontrovertible. Consequently,
he neglects to seriously consider a very real possibility: What
if human behavior is not determined by the physical domain? What
if his zombie (if it could exist), having only physical facts
but lacking a conscious mind, could not think, speak, or behave
as a conscious person? Perhaps the conscious mind is causally
necessary for reproducing human behavior at all! Chalmers does
not take this possibility seriously, and so we are left to ourselves
to consider the alternatives that could arise (an answer to epiphenomenalism)
by challenging not just materialism but scientific determinism
as well.

Nevertheless, The Conscious Mind goes a long way toward
re-instating serious discussions about consciousness. As the hard
problems of mind are taken seriously, we can expect richer and
more fruitful theories to emerge. Chalmers has taken the first
step. Perhaps the next step is to consider that mind, among all
of its other splendid mysteries, might also exert a causal influence
on the physical world. In this case, we shall have to take seriously
not just the our current picture of science but its inevitable
limitations as well. We may even live to see the day when free
will itself is resurrected as a topic worth taking seriously.
In this case, our picture of science will expand indeed.